<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>深入了解各种border-style类型</title>
  <style>
    .triangle {
      width: 0;
      height: 0;
      border-width: 20px;
      border-style: solid;
      border-color: red transparent transparent transparent
    }
    .triangle2 {
      width: 0;
      height: 0;
      border-width: 12px 20px;
      border-style:solid;
      border-color: red red transparent transparent;
    }
    .sharp1 {
      width: 0;
      height: 0;
      border-top: 20px solid lightblue;
      border-left: 10px solid transparent;
      border-right: 10px solid lightblue;
    }
  </style>
</head>
<body>

     <div class="triangle"></div>
     <div class="triangle2"></div>
     <div class="sharp1"></div>
</body>
</html>